A medical implant is any implant that embeds or attaches as a mechanical device or part in the tissues or organs of the body to achieve or enhance one or more biological functionality. In some cases such mechanical devices or parts may completely replace the function of the relevant body parts, such as tissues or organs, and more specifically, the bones, joints, ligaments, and muscles.
One universal requirement of implants, wherever they are used in the body, is the ability to form a suitably stable mechanical connection with neighboring hard or soft tissues. An unstable implant may function less efficiently, or cease functioning completely, which may induce excessive tissue response. In addition, it has been recognized that all implants should achieve a biological functionality, that is, the implant must meet several requirements for compatibility such as biological, mechanical, and morphological compatibility.
Depending on the primary function of the medical implant, the implant itself can take several forms. For example, in one form implants act as a load-bearing member instead, or in conjunction with, natural load-bearing members of the body such as bone. In such cases, a high strength material with an elastic modulus close to that of the bone which the implant is replacing or attaching to has been sought. In another form implants can be the whole or a part of articulating joints, such as a hip-joint. In such cases, materials with high wear and fretting resistance is desired. In still other forms implants can be cheek-bones, tooth implants, skull plates, fracture plates, intra-medullary rods, bone screws, etc.
Generally, the materials chosen for medical implants have been adapted for the use from materials developed for applications other than medical implants. As a result, such materials have not been always satisfactory. Moreover, the manufacturing of medical implants has also been a major issue as the fabrication of intricate shapes and surface finishing has either limited the desired functionality of such implants or increased the cost of making such implants substantially.
Accordingly, a new class of materials is needed to address the material and manufacturing deficiencies of current materials as well as to provide options and tailorable properties for the various demands of medical implants.